It’s over a century since the Grand Canyon was made a national park. Hard to believe that Americans once had to be encouraged to visit this natural wonder, but they did, and one of the people who did most to attract them in the early days was a Swedish watercolour painter, Gunnar Widforss. Researching a piece for last year to tie in with the anniversary (February 26, 2019), I followed the Widforss trail for Telegraph Travel. While I was in Arizona, I was lucky enough to meet Alan Petersen, who is curator of fine arts at the Museum of Northern Arizona, in Flagstaff, and who was then appealing for funds to complete a catalogue of Widforss’s works. That catalogue, which has taken him nearly 11 years of research and preparation, has now gone online; you can find it at www.gunnarwidforss.org.